Polymeric polythiols



Patented Jan. 24, 1950 POLYMERIC POLYTHIOLS Samuel L. Scott, Wilmington,Del., assignor to E. I. du Pont de Nemours & Company, Wilmington, DeL, acorporation of Delaware No Drawing. Application February 19, 1948,Serial No. 9,619

5 Claims- (01. 260-63) This invention relates to polymeric polythiolsand more particularly to new polymeric polythiols which are derived frommonoolefin/carbon monoxide polymers and to methods for theirpreparation.

Thiols and many other compounds containing one or more thiol groups arerecognized as being important classes of intermediates for organicsyntheses. ,The development and commercial utilization of simple andsubstituted thiols has been hindered, except for a few isolated cases,either by lack of suitable low cost raw materials or by unavailabilityof practical methods of preparation. It has been proposed, for example,to produce aliphatic thiols by the interaction of organic halogencompounds and sodium hydrosulfide or sodium thiosulfate. Although inseveral instances, particularly in the synthesis of primary thiols, thismethod gives good results, its commercial scope has been limited both bythe high cost and relative scarcity of suitable halogen compounds. Theliterature also contains disclosures of methods for the synthesis ofaliphatic thiols by addition of hydrogen sulfide to ethylenic compounds.Catalytic methods for the synthesis of thiols from organic sulfurcompounds containing reducible sulfur-oxygen, carbon-sulfur, andsulfur-sulfur groups or groups reducible to such groups, in the presenceof hydrogen sulfide, are also known. By these catalytic processes sulfurcontaining polymers in which the sulfur is intralinear can be cleaved tothiols.

It is an object of this invention to provide new and useful polymericpolythiols and methods for their preparation. A further object is toprovide new polymeric polythiols derived from monoolefin/ carbonmonoxide polymers. A still further obfeet is to provide new polymericpolythiols derived from ethylene/carbon monoxide polymers. Other objectswill appear hereinafter.

The objects of this invention are accomplished by providing polymericpolythiols which are the reaction products of the reductive-thiolationof a monoolefin/ carbon monoxide polymer with hydrogen and hydrogensulfide in which polymer the mole ratio of monoolefin to carbon monoxideis from 150:1 to 1:1. This invention provides new po ymeric polythiolsin which the thiol groups are present as lateral substituents on thepolymeric chain. Thus the polymeric polythiols of this invention have amain carbon chain and thiol groups as lateral substituents with thesulfur of said thiol groups directly attached to a carbon atom which isan integral part of said main carbon chain. The polymeric polythiol may2 also contain carbonyl carbon in the chain of contiguous carbon atomscomprising the main carbon chain of said polythiol.

The polymeric polythiols of this invention are prepared by subjecting amonoolefin/ carbon monoxide polymer in which the mole ratio ofmonoolefin to carbon monoxide is from :1 to 1:1 and preferably from 50:1to 1:1 to catalytic hydrogenation in the presence of hydrogen sulfide,or a substance yielding hydrogen sulfide under the conditions ofreaction, over a, sulfactive hydrogenation catalyst. As an illustrativeexample, a monoolefin/carbon monoxide polymer is charged into a highpressure reactor, together with hydrogen, an excess of hydrogen sulfide,and a sulfactive hydrogenation catalyst. The reactor is closed,agitated, and heated to a temperature at hich reaction occurs at asuitable rate. Additional hydrogen is added to the autoclave as neededto maintain the partial pressure of hydrogen in the autoclave in theneighborhood of 1000 1b./sq. in. After reaction is complete, asevidenced by cessation of hydrogen absorption, the autoclave is cooled,the catalyst is separated from the product, and the product isisolated.In the products of this invention at least some of the carbonyl groupsof the parent polymer have been replaced by thiol groups. Thesepolymeric polythiols contain at least 0.3% of thiol sulfur.

The monoolefin/ carbon monoxide polymers converted to polythiolsaccording to this invention are the products obtained by polymerizing amonoolefin containing up to and including our carbon atoms, such asethylene, propylene, isobutylene, or a plurality of said olefins, withcarbon monoxide in the presence of a polymerization catalyst, forexample, a peroxy compound, as disclosed and claimed in the applicationof M. M. Brubaker, U. S. Serial No. 552,374 filed September 1, 1944 andnow abandoned, of which Serial No. 97,908, filed June 8, 1949, is acontinuation-inpart. The monoolefin/ carbon monoxide polymers containthe carbonyl carbon in the chain of contiguous carbon atoms comprisingthe polymer chain.

Instead of charging hydrogen sulfide as such into the reactor there maybeused substances yielding hydrogen sulfide under the conditions ofreaction. For example, there may be used sulfur, carbon bisulfide, orsulfur dioxide. The proportion of hydrogen sulfide, or substancesyielding hydrogen sulfide used, may be varied considerably but it isdesirable to employ an excess over the amount theoretically required toconvert the carbonyl groups in the polymer to thiol groups.

In general, at least one mole of hydrogen sulfide, or an equivalentamount of a substance convertible to hydrogen sulfide, is employed percar-. bonyl group in the polymer.

The type of sulfactive catalyst employed may be varied considerably. Ingeneral the common hydrogenating metals as well as the subsulfides,sulfides, or polysulfides of such metals are efiective. Especiallyuseful are the sulfides and polysulfides of such metals as copper, iron,nickel, cobalt, lead, molybdenum, and the like. The metal sulfides maybe used as such or supported on a suitable carrier such as charcoal,kieselguhr, alumina, magnesia, silica, etc. Typical methods forpreparing these catalysts are described in U. S. Patents 2,402,683 and2,402,684 and include precipitation methods and sulfidation oi the metalor its compounds at ordinary or elevated temperatures by means ofsulfur, hydrogen sulfide, or other sulfur compounds. Th activity ofcertain of the metal sulfide catalysts may be improved by treatment withhydrogen at elevated temperatures.

The amount of sulfactive hydrogenation catalyst will be such as toprovide from 1 to 20% of active catalytic component, by weight of themonoolefin/carbon monoxide polymer. Generally, the amount used will befrom 5 to by weight of the monoolefin/carbon monoxide polymer.

In general, the process is operable at temperatures ranging from 75 to300 C. and at pressures of from atmospheric to a maximum determined bythe mechanical limitations of the equipment employed. It is preferred tooperate at a temperature of 100 to 250 C. and under a total pressure of1,000 to 15,000 lb./sq. in.

The examples which follow are submitted to illustrate and not to limitthis invention. All proportions are given in parts by weight, unlessotherwise designated.

Example I A stainless steel reaction vessel is charged with 64 parts ofsulfur, 100 parts of an ethylene/carbon monoxide polymer having amolecular weight of 1594 and containing ethylene and carbon monoxide inthe mole ratio of 5.79:1, and parts of cobalt sulfide hydrogenationcatalyst. The vessel is then closed, evacuated, and placed in a shaker Hmachine and connected to a source of high-pressure hydrogen. Hydrogen isexpanded into the reactor to give a pressure of 500 atm. Agitation isstarted, the temperature gradually raised to 150 C., and the pressureadjusted to 900 atm. I

The hydrogenation is continued for 14 hours, during which time theobserved pressure drop is 30 atm. The reactor is then allowed to cool;excess hydrogen and hydrogen sulfide are bled off; and the mixture ofproduct and catalyst is discharged. The reaction product is dissolved intoluene, and the solution filtered to remove the catalyst. The filtrateis then subjected to distillation to remove solvent. There is thusobtained a white, tacky, petrolatum-like product which analyzes 78.25%C, 12.23% H, and 3.85% S, and which has a molecu-' lar weight of 1140.The analytical data indicate that 23% of the carbonyl groups of theparent polymer are converted to thiol groups.

. Example II A stainless steel reaction vessel is charged with 64 partsof sulfur, 100 parts of an ethylene/carbon monoxide polymer containingethylene and carbon monoxide in the mole ratio of 4.32:1, and 20 partsof cobalt sulfide hydrogenation catalyst.

Cal

The vessel is closed, evacuated, placed in a shaker machine, andconnected to a source of high-pressure hydrogen. Hydrogen is expandedinto the reactor to a pressure of 500 atm., the temperature raisedgradually to 200 C., and the pressure adjusted to 800 atm. Theseconditions are maintained for 15 hours, during which time the observedpressure drop is 25 atm. The reactor is allowed to cool; excess hydrogenand hydrogen sulfide are bled off, and the mixture of polythiol andcatalyst discharged. The reaction mixture is diluted with benzene,warmed, purged with nitrogen to remove residual hydrogen sulfide, andilltered to remove the catalyst. Removal of the solvent from thefiltrate yields 60 parts of a viscous, straw-colored liquid whichanalyzes 76.72% C, 11.82% H, and 7.65% S. The composition data indicatethat 60% of the carbonyl groups of the parent polymer are converted tothiol groups.

Example III A stainless steel reaction vessel is charged with 64 partsof. sulfur, 100 parts of an ethylene/carbon monoxide polymer having amolecular weight of 1919 and containing ethylene and carbon monoxide inthe mole ratio of 2.36:1, and 20 parts of cobalt sulfide hydrogenationcatalyst. The vessel is closed, evacuated, placed in a shaker machine,and connected to a source of high-pressure hydrogen. Hydrogen isexpanded into the reactor to give a pressure of 500 atm. Agitation isstarted, the temperature gradually raised to 200 C., and the pressureadjusted to 800 atm. During a reaction period of 15 hours there is anobserved pressure drop of atm. The reactor is then allowed to cool;excess hydrogen and hydrogen sulfide are bled ofi; and the mixture ofproduct and catalyst is discharged. The reaction mixture is diluted withbenzene, warmed, purged with nitrogen to remove residual hydrogensulfide, and the solution is filtered to remove the catalyst. Removal ofthe solvent from the filtrate yields 78 parts of a viscous, brown liquidwhich analyzes 71.09% C, 10.00% H, and 14.79% S, and a molecular weightof 1698. From these data it may be calculated that 76% of the carbonylgroups in the original polymer were converted to thiol groups.

Example IV A stainless steel reaction vessel is charged with 64 parts ofsulfur, 100 parts of an ethylene/carbon monoxide polymer containingethylene and carbon monoxide in the mole ratio of 4.55:1, and 20 partsof cobalt sulfide hydrogenation catalyst. The vessel is closed,evacuated, placed in a shaker machine, and connected to a source ofhigh-pressure hydrogen. Hydrogen is expanded into the reactor to apressure of 490 atm. Agitation is started, the temperature graduallyraised to 200 C., and the pressure adjusted to 800 atm. During a 15-hourreaction period there is an observed pressure drop of atm. The reactoris allowed to cool; excess hydrogen and hydrogen sulfide are bled off;and the mixture of product and catalyst is discharged. The reactionmixture is diluted with benzene, warmed, purged with nitrogen to removeresidual hydrogen sulfide, and the solution is filtered to remove thecatalyst. Removal of the solvent from the filtrate yields 63 parts of asoft, sticky grease which analyzes 76.53% C, 11.92% H, and 7.99% S. Thecomposition data indicate that of the carbonyl groups in the originalpolymer were converted to thiol groups.

7 Example V A stainless steel reaction vessel is charged with 64 partsof sulfur, 100 parts of an ethylene/carbon monoxide polymer containingethylene and carbon monoxide in the mole ratio of 5.65:1. and 20 partsof cobalt sulfide hydrogenation catalyst. The vessel is then closed,evacuated. and placed in a shaker machine and connected to a source ofhigh-pressure hydrogen, and hydrogen is expanded into the reactor to apressure of 500 atm. Agitation is started, the temperature graduallyraised to 200 C., and the pressure adjusted to 800 atm. During a -hourreaction period there is an observed pressure drop of 40 atm. Thereactor is allowed to cool; excess hydrogen and hydrogen sulfide arebled ofi; and the mixture of product and catalyst is discharged. Thereaction mixture is diluted with benzene, warmed, purged with nitrogento remove residual hydrogen sulfide, and the solution filtered to removethe catalyst. Removal of the solvent from the filtrate yields '73 partsof a fluid, clear, straw-colored liquid which analyzes 77.14% C, 12.16%H, and 7.75% S.v The composition data indicate that 64% of the carbonylgroups have been converted to thiol groups.

Example VI parts of cobalt sulfide hydrogenation catalyst.

The vessel is closed, evacuated, placed in a shaker machine, andconnected to a source of high-pressure hydrogen. Hydrogen is expandedinto the reactor to give a pressure of 490 atm. Agitation is started,the temperature gradually raised to 200 C., and the pressure adjustedto' 800 atm. During a 15-hour reaction period there is. an observedpressure drop of atm. Thereactor is allowed to cool; excess hydrogen andhydrogen sulfide are bled off; and the mixture of product- Example VII Astainless steel reaction vessel is charged with 64 parts of sulfur, 100parts of an ethylene/carbon monoxide polymer having a molecular weightof 771 and containing ethylene and carbon monoxide in the mole ratio of5.90:1, and 20 parts of cobalt sulfide hydrogenation catalyst. Thevessel is closed, evacuated, placed in a'shaker machine, and connectedto a source of highnressure hydrogen. Hydrogen is expanded into thereactor to give a pressure of 500 atm. Agitation; is started, thetemperature gradually raised to 200 C., and the pressure adjusted to 800atm. During a 15-hour reaction period there is an observed pressure dropof 20 atm. The reactor is allowed to cool; excess hydrogen and hydrogensulfide are bled off; and the mixture of product and catalyst isdischarged. The reaction mixture is diluted with benzene, warmed, andpurged with nitrogen to remove residual hydrowas:

gen sulfide, and-the solution is filteredto remove th catalyst. Removalof the solvent from the filtrate yields 59 parts of a clear,straw-colored liquid which analyzes 76.86% C, 12.48% H, and 8.87% S, anda molecular weight of 635. The composition data indicate that 78% of thecarbonyl groups have been converted to thiol groups.

Example VIII A pressure reactor is charged with 33 parts of anethylene/carbon monoxide polymer, prepared as described below, 38 partsof sulfur, and 5 parts of a cobalt sulfide catalyst in parts of aceticacid and 100 parts or dioxane. The reactor is closed, and afterevacuation is placed in a shaker machine and connected to a source ofhigh pressure hydrogen. Hydrogen is expanded into the reactor so that at150 to 200 C. the pressure is between 1400 and 2000 lb./sq. in. During a6 hour reaction period there is an observed pressure drop of 1700lb./sq. in. The reactor is allowed to cool, bled of unreacted hydrogenand hydrogen sulfide, and discharged. The catalyst is separated byfiltration, and an aliquot of the product titrated for thiol sulfur. Thetitration indicates the presence of 0.037 equivalent of thiol sulfur.Evaporation of the solvent yields 12 parts oi! an amber, sticky resinanalyzing 5.5% thiol sulfur. This corresponds to a conversion of 13% ofthe carbonyl groups present in the original polymer to thiol groups.

The ethylene/carbon monoxide polymer used in the above example isprepared as follows: A pressure reactor is charged 100 parts of dioxane.and 1 part of benzoyl peroxide. The reactor is deoxygenated by sweepingit with oxygen-free nitrogen, and .is then pressured to 400 atm. withethylene and then to 500 atm. with carbon monoxide and then heated to100 C. During a 10.25- hour reaction period during which the pressure ismaintained at the indicated level by repressuringv with carbon monoxidethere is an indicated pressure drop of 80 atm. The reaction mixture issteam distilled to remove the dioxane. The product obtained weighs 333parts and melts at 93 to 94 C. and is waxy.

Example IX,

A stainless steel reactor is charged with twenty-five parts of anethylene/propylene/carbon monoxide polymer having a molecular weight of683 and an ethylene/propylene/ carbon monoxide mole ratio of1.26:0.6421, five parts of a cobalt sulfide hydrogenation catalyst, andthirty-two -parts of sulfur. The vessel is closed, evacuated, placed ina shaker machine, and connected to a source of high pressure hydrogen.Hydrogen is expanded into the reactor and the pressure adjusted so thatat 200 C. the pressure is between 860 and 910 atm. During a 15 hourreaction period there is an observed pressure drop of 50 atm. Thereactor is allowed to cool, bled of unreacted hydrogen and hydrogensulfide, and discharged. The reaction mixture is diluted with 6;toluene, warmed, and then filtered to remove the catalyst. Removal ofthe solvent from the filtrate yields 11 parts of a mobile oil having amolecular weight of 647 and analyzing 71.49% C, 10.84% H, and 13.73% S.From these data it may be calculated that 78% of the carbonyl groups ofthe original polymer were converted to thiolgroups.

The cobaltsulfide catalyst used in the above examples was prepared asfollows: 7 Two hundred eighty parts of sodium disulfide monohydrate isdissolved in 1750 parts of water and 75 parts of sulfur is then added tothe solution with stirring until solution is complete. The solution isthen filtered and added with continuous stirring, during a period of 10minutes, to a solution of 282 parts of cobaltic chloride hexahydrate in1750 parts of water. Stirring is continued for minutes after completionof the addition. The precipitate which forms is filtered with suctionand washed with water on the filter until the filter water is clear.Surface water is sucked oil and the precipitate on the filter is thentreated with 350 parts of denatured ethyl alcohol and the precipitatesucked dry. The dry cake is transferred to a receptacle and dispersed in3500 parts of denatured ethyl alcohol. The slurry is then filtered andthe product sucked dry on the filter. The cake is transferred to avacuum drier and dried under vacuum for 24 hours at steam bathtemperature. The flask is allowed to cool, the vacuum is ruptured andthe dried cobalt sulfide wet with benzene. The wet cobalt sulfide isthen ground to a fine powder. It is stored in containers with air-tightclosures since it is pyrophoric.

A typical preparation of a monoolefin/carbon monoxide polymer, e. g., anethylene/carbon monoxide polymer employable in the practice of thisinvention is the following: A pressure reactor is swept free of air withdeoxygenated nitrogen, charged with 3 parts of di(tertiary butyl)peroxide and 100 parts of cyclohexane, closed and evacuated. The reactoris then placed in a heated shaker box, and connected to a high pressuresource of mixed gas containing 88% ethylene and 12% carbon monoxide.Ethylene/ carbon monoxide gas is expanded into the reactor to a pressureof 40 atm., and heating and agitation are started. The temperature ofthe reaction mixture is raised to 135 C. and maintained in the range of130 to 140 C. for 15 hours, during which time the pressure is adjustedto about 133 atm. by repressuring with the ethylene/carbon monoxide gasmixture. The vessel is then cooled, excess ethylene and carbon monoxideare bled off, and the vessel is opened. The reaction product comprises amixture of ethylene/carbon monoxide polymer and cyclohexane. The removalof the cyclohexane by distillation leaves the ethylene/carbon monoxidepolymer as a nonvolatile residue. Sixty parts of a white, tacky,beeswax-like product melting at 60 to 95 0., and containing ethylene andcarbon monoxide in a mole ratio of 5:1, is obtained.

If desired, a minor amount of another polymerizable monomer can beincluded with the monoolefin, or monoolefins and carbon monoxide in thepolymerization charge. Examples of such other polymerizable monomers arevinyl compounds, e. g., vinyl chloride, vinyl acetate, styrene,vinylidene compounds, e. g., methyl methacrylate, methyl acrylate,vinylidene chloride, vinylene compounds, e. g., dimethyl maleate, maleicanhydride, etc.

In place of the catalysts heretofore mentioned, there may be usedruthenium catalysts either as finely divided ruthenium metal or in theform of its oxide or salts. The ruthenium catalyst may be supported orit may be unsupported. A suit able method for preparing, for example, acharcoal supported ruthenium catalyst consists in fusing ruthenium orits oxide with sodium peroxide, dissolving the salt, pouring theresulting solution over charcoal and drying the impregnated charcoal.Other methods, however,

may be used such as that of U. 8. Patent 2,079,404 or other proceduresbased on the reduction of a compound of ruthenium in the presence of acarrier substance.

Although in the examples there are indicated certain definite conditionsof temperature, pressure, concentration, duration of reaction, catalystconcentration, etc., it is to be understood that these may be variedsomewhat within the scope of this invention since the conditions of eachexperiment are determined by the particular monoolefin/carbon monoxidepolymer treated, the quantity employed, and the catalyst used.

The hydrogenation of the monoolefin/carbon monoxide polymers in thepresence of hydrogen sulfide may be carried out in the presence orabsence of solvents. Suitable solvents include dioxane, saturatedaliphatic and cycloaliphatic hydrocarbons, and the like.

The process of this invention may be carried out either as a batch or asa semi-continuous or continuous operation.

By the process of this invention there may be prepared secondary thiolsin which the thiol groups are present as lateral substituents on thepolymer chain.

The polymeric polythiols produced in accord with this invention may beoxidized to polysulfonic acids or to polysulfides which are useful perse as wool lubricants, etc. or as intermediates for other syntheses. I

As many apparently widely different embodiments of this invention may bemade without departing from the spirit and scope thereof, it is to beunderstood that this invention is not limited to'the specificembodiments thereof except as defined in the appended claims.

I claim:

1. A polymeric polythiol which is the reaction product-of thereductive-thiolation with hydrogen and hydrogen sulfide at a temperatureof 75 to 300 C. of a polymer of 1 molar equivalent of carbon monoxideand from 1 to molar equivalents of a monoolefin containing from 2 to 4carbon atoms, said polymeric polythiol having a main chain of contiguouscarbon atoms and having thiol groups as lateral substituent groupsthereon with the sulfur of each thiol group directly attached solely tohydrogen and to a carbon atom which is an integral part of said mainchain of contiguous carbon atoms.

2. A polymeric polythiol which is the reaction product of thereductive-thiolation with hydrogen and hydrogen sulfide at a temperatureof 75 to 300 C. of a. polymer of 1 molar equivalent of carbon monoxideand from 1 to 150 molar equivalents of a monoolefin containing from 2 to4 carbon atoms, said polymeric polythiol having a main chain ofcontiguous carbon atoms containing carbonyl carbon therein and havingthiol groups as lateral substituent groups thereon with the sulfur ofeach thiol group directly attached solely to hydrogen and to a carbonatom which is an integral part of said main chain of contiguous carbonatoms.

3. A polymeric polythiol which is the reaction product of thereductive-thiolation with hydrogen and hydrogen sulfide at a temperatureof 75 to 300 C. of a polymer of 1 molar equivalent of carbon monoxideand from 1 to 150 molar equivalents of ethylene, said polymericpolythiol having a main chain of contiguous carbon atoms and havingthiol groups as lateral substituent groups thereon with the sulfur ofeach thiol group directly attached solely to hydrogen and-to a carbonatom which is an integral part of said main chain of contiguous carbonatoms.

4. A polymeric polythiol which is the reaction product of thereductive-thiolation with hydrogen and hydrogen sulfide at a temperatureof 75 to 300 C. of a polymer of 1 molar equivalent of carbon monoxideand from 1 to 150 molar equivalents.

of ethylene, said polymeric polythiol having a main chain of contiguouscarbon atoms containing carbonyl carbon therein and having thiol 10 bonmonoxide and from 1 to 50 molar equivalents of ethylene, said polymericpolythiol having a. main chain of contiguous carbon atoms containingcarbonyl carbon therein and having thiol groups as lateral substituentgroups thereon with the sulfur of each thiol group directly attachedsolely to hydrogen and to a carbon atom which is an integral part ofsaid main chain of contiguous carbon atoms.

SAMUEL L. SCOTT.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,402,614 Farlow June 25, 19462,411,954 Burke Dec. 3, 1946

1. A POLYMERIC POLYTHIOL WHICH IS THE REACTION PRODUCT OF THEREDUCTIVE-THIOLATION WITH HYDROGEN AND HYDROGEN SULFIDE AT A TEMPERATUREOF 75* TO 300*C. OF A POLYMER OF 1 MOLAR EQUIVALENT OF CARBON MONOXIDEAND FROM 1 TO 150 MOLAR EQUIVALENTS OF A MONOOLEFIN CONTAINING FROM 2 TO4 CARBON ATOMS, SAID POLYMERIC POLYTHIOL HAVING A MAIN CHAIN OFCONTIGUOUS CARBON ATOMS AND HAVING THIOL GROUPS AS LATERAL SUBSTITUENTGROUPS THEREON WITH THE SULFUR OF EACH THIOL GROUP DIRECTLY ATTACHEDSOLELY TO HYDROGEN AND TO A CARBON ATOM WHICH IS AN INTEGRAL PART OFSAID MAIN CHAIN OF CONTIGUOUS CARBON ATOMS.